The invention relates on the one hand to an arrangement and on the other to a method for diagnosing malignant tissue by fluorescence observation using an endoscope which comprises a white light source, a fluorescence stimulator emiting a light beam, and an analyzer.
With endoscopic tumor diagnosis, one can differentiate between direct and indirect signs of tumors. A direct sign of a tumor can be recognized by the tumor mass itself. An indirect sign of a tumor is for example an irregular course of vessels. According to the picture of disease and disease stage of the tissue, however, the indirect sign of a tumor becomes less specific. Early cancers, that is X-ray negative tissue change and tissue change which can no longer be endoscopically differentiated from healthy tissue, may then only be diagnosed with difficulty. Here, one uses fluorescence examinations in order to determine in healthy surroundings, cell or tissue structures. With this, one evaluates the differing fluorescence behavior of healthy and diseased tissue. Apart from the measuring and evaluation of autofluorescence, it is also known to enhance the contrast by enrichment with photosensitive substances with a strong affinity to malignant tissue. Here, one is concerned with medication-induced fluorescence or photodynamic diagnostics. These substances are stored in malignant tissue longer than in the healthy surroundings. With light exposure in the ultra-violet to the infra-red region, which is usually produced by a laser, the fluorescence is stimulated. An analysis of the wave length of the fluorescence, which is emitted by the damaged tissue makes possible the diagnosis of tumors. The autofluorescence and the medication-induced fluorescence thus makes possible further information, which may not be determined with the naked eye.
U.S. Pat. No. 4,556,057 discloses means for carrying out an endoscopic tumor diagnosis including means for stimulating the fluorescence, for spectral analysis and the necessary laser apparatus. With this an endoscope with an optical fiber is introduced into a body cavity and the tissue to be examined is irradiated with a pulsating laser light. The fluorescence light induced is then measured and evaluated in order to determine whether a tissue is normal or diseased. Diseased tissue may then be destroyed by a high laser energy through the same optical fiber.
The examination is carried out in the monochromatic light spectrum, with which fluorescence can be stimulated. A picture may be drawn up of the diseased tissue. For this an image intensifier is necessary since the interesting fluorescence signal is several powers of ten lower than that which the naked eye can perceive.
A simultaneous observation with white light may not be carried out. In order to locally pinpoint possibly diseased tissue, a white light source is provided, which can be controlled alternately with the pulsed laser beam.
A simultaneous evaluation of the optically indirect tumor signs and the fluorescent tumor signs has not been possible up to now. This however would be desired, since for example dysplasia and inflammation have fluorescence. Furthermore the whole diagnosis procedure and the probing in the body cavity would be made easier or improved.
The known arrangement is also not suitable for examining tumors with autofluorescence, since the energy of the light used for fluorescence stimulation may not be limited. This is required because the cells lose the fluorescent ability when a monochromatic light for fluorescence stimulation of biological tissue exceeds a certain energy or intensity peak. The loss of fluorescent ability is called bleaching.